JP6977276B2 - Image forming apparatus and its control method and program - Google Patents

Description

The present invention relates to an image forming apparatus provided with a photoconductor, a control method thereof, and a program.

In an electrophotographic image forming apparatus, a cleaning member, a charging roller, or the like is in sliding contact with the surface of a photoconductor, so that an electric charge is generated inside the photoconductor, and the generated electric charge remains inside the photoconductor and is chargeable. It is known to cause deterioration and ghosting. As a technique for solving such a problem, Patent Document 1 describes a technique for removing internal residual charges by exposing a photoconductor with a larger exposure amount than at the time of image formation when the power of the image forming apparatus is turned on. Is disclosed. Further, in Patent Document 2, at the time of non-image formation, the internal residual charge is removed by charging the photoconductor once or more with the developing roller separated from the photoconductor and the transfer bias and the static eliminator turned off. The technology to be used is disclosed.

Japanese Unexamined Patent Publication No. 2002-162876 Japanese Unexamined Patent Publication No. 2016-142856

However, there is a possibility that the internal residual charge cannot be sufficiently removed by the prior art.

Therefore, an object of the present invention is to provide an image forming apparatus capable of sufficiently removing the internal residual charge of the photoconductor, a control method thereof, and a program.

In order to solve the above problems, the image forming apparatus according to the present invention has a photoconductor having a photosensitive layer, a charger that charges the surface of the photoconductor to the first polarity, and a surface of the photoconductor having the first polarity. It includes a reverse charging device that charges to the second polarity opposite to the above, an exposure device that exposes the surface of the photoconductor, a developer that supplies a developer to the photoconductor, and a control device.
In the control device, the surface of the photoconductor is charged to the first polarity by the charger, and the surface of the photoconductor charged by the first charge process is exposed by the photographic processor. A first exposure process for forming an electrostatic latent image on the surface, and a developing process for supplying a developer to the electrostatic latent image by the developer to form a developer image on the surface of the photoconductor. In a period different from the transfer process of transferring the developer image to the transfer medium and the execution period of the transfer process, at least one rotation of the photoconductor causes the surface of the photoconductor to be surfaced by the reverse charging device. During the period during which the polar charging process and the portion of the photoconductor charged to the second polarity by the reverse charging process pass through the position facing the developing device, the photosensitivity is emitted from the developing device. At least during the period in which the supply of the developer to the body is stopped and the portion of the photoconductor charged to the second polarity by the back charge process passes through the position facing the exposure apparatus. A second exposure process in which the surface of the photoconductor is exposed by the photographic processor while the photoconductor makes one revolution, and a position where the portion of the photoconductor exposed by the second exposure process faces the charger. During the passing period, a second charging process of charging the surface of the photoconductor to the first polarity by the charger is performed for at least one rotation of the photoconductor.

According to this configuration, by performing the back charge treatment and the second exposure treatment for at least one rotation of the photoconductor, a second electric field corresponding to the second polarity can be applied over the photosensitive layer all around the photoconductor. At the same time, the charge of the first polarity generated by the exposure can be moved by the second electric field to remove the charge of the second polarity among the internal residual charges. Then, when the surface of the photoconductor is charged to the first polarity by the second charging process, the first electric field corresponding to the first polarity can be applied to the photosensitive layer all around the photoconductor, so that it is generated by exposure. The charge of the second polarity can be moved by the first electric field to remove the charge of the first polarity among the internal residual charges.

Further, in the control method according to the present invention, a photoconductor having a photosensitive layer, a charger that charges the surface of the photoconductor to the first polarity, and a second surface of the photoconductor having the opposite polarity to the first polarity. Control by the control device in an image forming apparatus including a reverse charging device that charges polarly, an exposure device that exposes the surface of the photoconductor, a developer that supplies a developer to the photoconductor, and a control device. The method.
The control method includes a first charging step in which the surface of the photoconductor is charged to the first polarity by the charger, and the surface of the photoconductor charged by the first charging process is exposed by the photographic processor. A first exposure step of forming an electrostatic latent image on the surface, and a developing step of supplying a developer to the electrostatic latent image by the developer to form a developer image on the surface of the photoconductor. In a period different from the transfer step of transferring the developer image to the transfer medium and the execution period of the transfer process, at least one rotation of the photoconductor causes the surface of the photoconductor to be surfaced by the reverse charging device. During the period during which the polar charging step and the portion of the photoconductor charged to the second polarity by the back charging step pass through the position facing the developing device, the photosensitivity is emitted from the developing device. At least during the period in which the supply of the developer to the body is stopped and the portion of the photoconductor charged to the second polarity by the reverse charging step passes through the position facing the exposure apparatus. The second exposure step of exposing the surface of the photoconductor by the exposure apparatus while the photoconductor makes one rotation, and the position where the portion of the photoconductor exposed by the second exposure step faces the charger. It comprises a second charging step of charging the surface of the photoconductor to the first polarity by the charger during at least one rotation of the photoconductor during the passage.

According to this control method, by performing the back charge step and the second exposure step for at least one rotation of the photoconductor, a second electric field corresponding to the second polarity can be applied over the photosensitive layer all around the photoconductor. At the same time, the charge of the first polarity generated by the exposure can be moved by the second electric field to remove the charge of the second polarity among the internal residual charges. Then, when the surface of the photoconductor is charged to the first polarity by the second charging step, the first electric field corresponding to the first polarity can be applied to the photosensitive layer all around the photoconductor, so that it is generated by exposure. The charge of the second polarity can be moved by the first electric field to remove the charge of the first polarity among the internal residual charges.

Further, the program according to the present invention includes a photoconductor having a photosensitive layer, a charger that charges the surface of the photoconductor to the first polarity, and a second polarity opposite to the first polarity on the surface of the photoconductor. The control device is operated in an image forming device including a back-charging device for charging the photoconductor, an exposure device for exposing the surface of the photoconductor, a developer for supplying a developer to the photoconductor, and a control device. It is a program to let you.
In the program, the control device is subjected to a first charging process of charging the surface of the photoconductor to the first polarity by the charger, and a surface of the photoconductor charged by the first charging process. Is exposed by the exposure apparatus to perform a first exposure process for forming an electrostatic latent image on the surface, and a developer is supplied to the electrostatic latent image by the developing device to form a surface of the photoconductor. A means for executing a developing process for forming a developer image on the surface, a means for executing a transfer process for transferring the developer image to a transfer medium, and at least the photoconductor in a period different from the execution period of the transfer process. A means for executing a back-charging process in which the surface of the photoconductor is charged to the second polarity by the back-charging device and the photoconductor charged in the second polarity by the back-charging process. A means for executing a stop process for stopping the supply of the developer from the developer to the photoconductor while the portion of the surface is passing through a position facing the developer, and the second counter-charge process. The surface of the photoconductor is exposed by the photographic processor at least while the photoconductor makes one revolution while the portion of the photoconductor that is polarly charged passes through the position facing the photographic processor. 2 The means for executing the exposure process and the period during which the portion of the photoconductor exposed by the second exposure process passes through a position facing the charger, at least while the photoconductor makes one revolution. The surface of the photoconductor is made to function as a means for performing a second charging process of charging the surface of the photoconductor to the first polarity by the charger.

According to this program, by performing the back charge treatment and the second exposure treatment for at least one rotation of the photoconductor, a second electric field corresponding to the second polarity can be applied over the photosensitive layer all around the photoconductor. At the same time, the charge of the first polarity generated by the exposure can be moved by the second electric field to remove the charge of the second polarity among the internal residual charges. Then, when the surface of the photoconductor is charged to the first polarity by the second charging process, the first electric field corresponding to the first polarity can be applied to the photosensitive layer all around the photoconductor, so that it is generated by exposure. The charge of the second polarity can be moved by the first electric field to remove the charge of the first polarity among the internal residual charges.

According to the present invention, the internal residual charge of the photoconductor can be sufficiently removed.

It is sectional drawing which shows the color printer which concerns on 1st Embodiment of this invention. It is a figure explaining the separation between a photoconductor drum and a developing roller. It is a figure which shows the structure of a control device and the like. It is a figure which shows the arrangement relation of the member around the photoconductor drum. It is a figure (a), (b) which shows the principle that the residual charge is generated inside a photosensitive layer. It is a figure (a)-(e) which shows the principle of removing a residual charge. It is a flowchart which shows the operation of a control device. It is a flowchart which shows the residual charge removal process. It is a time chart which shows the operation of a control device. It is a figure (a)-(h) which shows the process which a residual charge is removed. It is a time chart which shows the operation of the control device which concerns on 2nd Embodiment. It is a flowchart which shows the operation of the control device which concerns on 2nd Embodiment. It is a time chart which shows the operation of the control device which concerns on 3rd Embodiment. It is a flowchart which shows the operation of the control device which concerns on 3rd Embodiment. It is a time chart which shows the operation of the control device which concerns on 4th Embodiment.

[First Embodiment]
Next, the first embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, the overall configuration of a color printer as an example of an image forming apparatus will be described, and then the characteristic portions of the present invention will be described in detail.

In the following description, the direction of the color printer is "front side" when facing the paper surface in FIG. 1, "rear side" when facing the paper surface, "left side" when facing the paper surface, and facing the paper surface. The front side is the "right side". In addition, the vertical direction toward the paper surface is defined as the "vertical direction".

As shown in FIG. 1, the color printer 1 has a paper feed unit 20 that supplies paper P as an example of a transfer medium, and an image forming unit that forms an image on the paper P that has been fed. 30 and a paper ejection unit 90 for ejecting the paper P on which the image is formed are provided.

The paper feed unit 20 includes a paper feed tray 21 for accommodating the paper P and a paper transfer device 22 for transporting the paper P in the paper feed tray 21 to the image forming unit 30.

The image forming unit 30 is mainly composed of a scanner 40 as an example of an exposure device, a plurality of process units 50, a transfer unit 70, a cleaning device 60, and a fixing unit 80.

The scanner 40 is arranged above the plurality of process units 50, and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, and the like, which are indicated by omitting reference numerals. Then, in the scanner 40, the laser beam is reflected by a polygon mirror or a reflecting mirror, is emitted by passing through a lens, and is irradiated on the surface of a photoconductor drum 51 as an example of a photoconductor by high-speed scanning. ..

The plurality of process units 50 are arranged side by side in the front-rear direction. The process unit 50 includes a drum unit 510 and a developer 520 that can be attached to and detached from the drum unit 510.

The drum unit 510 includes a photoconductor drum 51, a charging roller 52 as an example of a reverse charging device and a charging device, and a cleaning blade 57. The developer 520 includes a developing roller 54, a supply roller 55, and a toner accommodating chamber 56 for accommodating toner as an example of a developer.

The process units 50, which contain toners of black, yellow, magenta, and cyan, are arranged in this order from the upstream in the transport direction of the paper P, which are indicated by the codes of 50K, 50Y, 50M, and 50C. In the present specification and drawings, when the photoconductor drum 51, the developing roller 54, etc. corresponding to the toner color are specified, they correspond to black, yellow, magenta, and cyan, respectively, and K, Y, and M are used. , C symbol will be added.

As shown in FIG. 3, the photoconductor drum 51 has a cylindrical raw tube 51A and a photosensitive layer 51B formed on the outer peripheral surface of the raw tube 51A. The raw tube 51A is made of a conductive member such as metal. The photosensitive layer 51B is formed of a positively charged organic photosensitive layer in which a charge generating material, an electron transporting material, and a hole transporting material are dispersed in a resin. The raw tube 51A is connected to the ground potential of the color printer 1.

The charging roller 52 is a roller that charges the surface of the photoconductor drum 51. The charging roller 52 is in contact with the surface of the photoconductor drum 51. A positive charging voltage is applied to the charging roller 52 at the time of charging.

The developing roller 54 comes into contact with the photoconductor drum 51 and supplies toner to the electrostatic latent image on the photoconductor drum 51 to develop the electrostatic latent image with toner. In the present embodiment, when the toner is supplied from the developing roller 54 to the photoconductor drum 51, the toner is positively charged due to the toner being slidably contacted between the developing roller 54 and the supply roller 55. It is supposed to be done.

As shown in FIG. 2, the developing roller 54 can be brought close to and separated from the photoconductor drum 51 by controlling the contact / detachment mechanism TM by the control device 100. Specifically, in the color mode, all the developing rollers 54K, 54Y, 54M, 54C come into contact with the corresponding photoconductor drums 51K, 51Y, 51M, 51C, respectively, and the respective photoconductor drums 51K, 51Y, 51M, 51C. It is designed to supply toner to the drum. Further, in the monochrome mode, only the black developing roller 54K comes into contact with the photoconductor drum 51K, and the other three color developing rollers 54Y, 54M, 54C are separated from the corresponding photoconductor drums 51Y, 51M, 51C. It has become like. Further, in the residual charge removing process described later, all the developing rollers 54K, 54Y, 54M, 54C are separated from the corresponding photoconductor drums 51K, 51Y, 51M, 51C, respectively.

As shown in FIG. 1, the cleaning blade 57 is a member that collects foreign matter such as toner adhering to the surface of the photoconductor drum 51. The cleaning blade 57 is in contact with the surface of the photoconductor drum 51.

The transfer unit 70 is provided between the paper feed unit 20 and each process unit 50, and includes a drive roller 71, a driven roller 72, a transfer belt 73, and a transfer roller 74 as an example of a transfer member. ..

The drive roller 71 and the driven roller 72 are arranged in parallel so as to be separated from each other in the front-rear direction, and a transport belt 73 made of an endless belt is stretched between them. The outer surface of the transport belt 73 is in contact with each photoconductor drum 51. Further, inside the transport belt 73, four transfer rollers 74 that sandwich the transport belt 73 with each photoconductor drum 51 are arranged so as to face each photoconductor drum 51. A negative transfer voltage is applied to the transfer roller 74 during transfer.

The charging roller 52, the developing roller 54, the transfer roller 74, and the cleaning blade 57 provided around the photoconductor drum 51 are arranged in this order in the rotation direction of the photoconductor drum 51.

The cleaning device 60 is a device that is in sliding contact with the transport belt 73 and collects toner or the like adhering to the transport belt 73, and is arranged so as to face the lower side of the transport belt 73.

The fixing unit 80 is arranged behind each process unit 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 arranged to face the heating roller 81 and press the heating roller 81.

In the image forming unit 30 configured in this way, first, the surface of each photoconductor drum 51 is uniformly positively charged by the charging roller 52, and then exposed by the scanner 40. As a result, positive and negative charges are generated inside the photosensitive layer 51B (see FIG. 3), and the negative charges are transported to the surface, so that the positive charges charged on the surface are canceled by the negative charges. , An electrostatic latent image is formed. After that, the toner in the developer 520 is supplied to the electrostatic latent image on the photoconductor drum 51 by the developing roller 54, so that the toner image is supported on the photoconductor drum 51.

Next, the paper P supplied on the transport belt 73 passes between each photoconductor drum 51 and each transfer roller 74, so that the toner image supported on each photoconductor drum 51 is transferred onto the paper P. Transferred. Then, the paper P passes between the heating roller 81 and the pressure roller 82, so that the toner image transferred on the paper P is heat-fixed.

The paper ejection unit 90 mainly includes a plurality of transport rollers 91 for transporting the paper P. The paper P to which the toner image is transferred and heat-fixed is conveyed by the conveying roller 91 and discharged to the outside of the main body housing 10.

As shown in FIG. 3, the color printer 1 includes a control device 100, a charging voltage applying circuit 210, a drum driving mechanism 220, a developing voltage applying circuit 230, and a transfer voltage applying circuit 240.

The charging voltage application circuit 210 can apply a positive first charging voltage and a second charging voltage as an example of the first polarity to each charging roller 52, and as an example of the second polarity. It is a circuit that can apply a negative reverse charge voltage. When a first charging voltage or a second charging voltage is applied to the charging roller 52, the surface of the photoconductor drum 51 is positively charged, and when a reverse charging voltage is applied to the charging roller 52, the surface of the photoconductor drum 51 is negatively charged. Is designed to be charged.

The drum drive mechanism 220 is a mechanism for rotating the photoconductor drum 51, and includes a motor, a gear, a clutch, and the like.

The development voltage application circuit 230 is a circuit that applies a positive development bias to each development roller 54. The development bias at the time of printing is set to a value lower than the charging voltage and higher than the surface potential of the exposed portion of the photoconductor drum 51. The transfer voltage application circuit 240 is a circuit that applies a negative transfer voltage to each transfer roller 74.

The control device 100 has a CPU, ROM, RAM, etc., and according to a program prepared in advance, the above-mentioned paper feed unit 20, image forming unit 30, paper ejection unit 90, etc. are used in response to reception of a print command or the like. It is configured to control. The control device 100 can mainly execute an image forming process for forming a toner image on the paper P and a residual charge removing process for removing the residual charge remaining in the photosensitive layer 51B of the photoconductor drum 51. .. When performing each process, the control device 100 rotates the photoconductor drum 51 and the like via the drum drive mechanism 220.

Here, the residual charges are positive and negative charges generated in the photosensitive layer 51B when the photoconductor drum 51 is in sliding contact with the cleaning blade 57 or the like. As shown in FIGS. 5A and 5B, the residual charges C1 and C2 gradually increase each time the photoconductor drum 51 slides into contact with the cleaning blade 57 or the like. Since the residual charges C1 and C2 are charges that are difficult to move freely, it is considered that they are difficult to move from the field even if an electric field acts during charging, and are deposited near the surface of the photosensitive layer 51B. There is.

The control device 100 executes a first charge process, a first exposure process, a development process, and a transfer process in the image forming process, and a reverse charge process, a stop process, and a second in the residual charge removal process. The exposure process and the second charge process are performed. In other words, the control device 100 functions as a means for executing each of the above-mentioned processes by operating based on the program. Further, the control method by the control device 100 includes a step of executing each of the above-mentioned processes.

The first charging process is a process in which the surface of the photoconductor drum 51 is positively charged by the charging roller 52. Specifically, the first charging process is a process for executing the first exposure process based on the image data described later. That is, the first charging process is a process for charging the portion of the photoconductor drum 51 facing the scanner 40 to an appropriate surface potential from the start to the end of the first exposure process.

Here, as shown in FIG. 4, the first position P1 facing the charging roller 52 on the surface of the photoconductor drum 51 is a photoconductor rather than the second position P2 facing the scanner 40 on the surface of the photoconductor drum 51. It is located on the upstream side of the drum 51 in the rotation direction. Further, the first position P1 is separated from the second position P2 by a second distance D2 in the circumferential direction of the photoconductor drum 51. Therefore, the second time T2 until the portion charged by the charging roller 52 reaches the second position P2 can be expressed by the following equation (1).
T2 = D2 / S ... (1)
D2: The circumference of the portion of the surface of the photoconductor drum 51 including the first position P1 and the second position P2, downstream of the first position P1 and upstream of the second position P2. Length S: Peripheral speed of the photoconductor drum 51

Therefore, as shown in FIG. 9, the first charging process is performed at least from a time point (time t10) two hours before the start of the first exposure process by a second time T2, and a second time from the end of the first exposure process. It suffices if it is executed at the time TF up to the time point (time t12) before T2. In the present embodiment, the first charging process is executed from the time t7 before the time t10 to the time t15 after the time t12.

In the first charging process, the control device 100 applies the first charging voltage to the charging roller 52 via the charging voltage application circuit 210. More specifically, the control device 100 outputs a control signal corresponding to the first charge voltage to the charge voltage application circuit 210 based on the reception of the print command. The charging voltage application circuit 210 applies the first charging voltage to the charging roller 52 according to the control signal output from the control device 100. In this embodiment, the first charging voltage is set to a predetermined value V11. The predetermined value V11 is set to, for example, 1500V.

Further, in the present embodiment, the control device 100 ends the first charging process after the lapse of the third time T3 from the end of the transfer process described later. Here, the third time T3 can be expressed by the following equation (2).
T3 = D3 / S ... (2)
D3: A portion of the surface of the photoconductor drum 51 including the first position P1 and the fourth position P4 (see FIG. 4) facing the transfer roller 74, downstream of the fourth position P4, and Perimeter of the portion upstream of the first position P1 S: Perimeter of the photoconductor drum 51

By continuing the first charging process for the third time T3 from the end of the transfer process in this way, it becomes possible to end printing with the surface potential of the photoconductor drum 51 substantially uniform. There is.

The first exposure process is a process of exposing the surface of the photoconductor drum 51 charged by the first charge process with a scanner 40 to form an electrostatic latent image on the surface. In the first exposure process, the control device 100 blinks the scanner 40 based on the image data corresponding to the print command to form an electrostatic latent image on the surface of the photoconductor drum 51. The execution time of the first exposure process varies depending on the amount of image data. Further, the execution time of the first charging process and the like described above also fluctuate according to the fluctuation of the execution time of the first exposure process.

The developing process is a process in which toner is supplied to the electrostatic latent image by the developing roller 54 to form a toner image on the surface of the photoconductor drum 51. The control device 100 applies a developing voltage to the developing roller 54 via the developing voltage applying circuit 230 in the developing process. The development voltage is set to, for example, 300V.

The transfer process is a process of transferring the toner image to the paper P. The control device 100 applies the first transfer voltage to the transfer roller 74 via the transfer voltage application circuit 240 in the transfer process. Further, the control device 100 ends the transfer process after the lapse of the first time T1 after the first exposure process is completed. Here, the first time T1 can be expressed by the following equation (4).
T1 = D1 / S ... (4)
D1: A portion of the surface of the photoconductor drum 51 including the second position P2 and the fourth position P4 (see FIG. 4) facing the transfer roller 74, downstream of the second position P2, and Perimeter of the portion upstream of the fourth position P4 S: Perimeter of the photoconductor drum 51

The back charge process is a process in which the surface of the photoconductor drum 51 is negatively charged by the charging roller 52 while the photoconductor drum 51 makes one rotation in a period different from the execution period of the transfer process. In the back charge process, the control device 100 applies a back charge voltage having a polarity opposite to that of the first charge voltage to the charge roller 52 via the charge voltage application circuit 210. In this embodiment, the reverse charge voltage is set to the specified value −V12. The absolute value of the specified value −V12 can be, for example, the same value as the predetermined value V11 described above. The specified value -V12 is set to, for example, -1500V.

The control device 100 starts the back charge process during the stop process described later. Specifically, the control device 100 starts the back charge process when the print command is received. In other words, the control device 100 starts the back charge process after stopping the supply of toner from the developer 520 to the photoconductor drum 51 by the stop process.

The stop treatment is performed from the developing roller 54 to the photoconductor during the period in which the portion of the photoconductor drum 51 that is negatively charged by the back charge treatment passes through the third position P3 (see FIG. 4) facing the developing roller 54. This is a process for stopping the supply of toner to the drum 51. Specifically, the control device 100 separates the developing roller 54 from the photoconductor drum 51 by controlling the contact / detachment mechanism TM in the stop processing.

The control device 100 starts the stop process after the transfer process is completed. Specifically, the control device 100 starts the stop process after the end of the first charge process (time t15: see FIG. 9). Further, the control device 100 ends the stop process after the lapse of the fourth time T4 from the start of the first charge process (time t7: see FIG. 9), and brings the developing roller 54 into contact with the photoconductor drum 51. Here, the fourth time T4 can be expressed by the following equation (3).
T4 = D4 / S ... (3)
D4: A portion of the surface of the photoconductor drum 51 including the first position P1 and the third position P3 (see FIG. 4) facing the developing roller 54, downstream of the first position P1 and on the downstream side. Perimeter of the portion upstream of the third position P3: Perimeter of the photoconductor drum 51

Thereby, when the portion of the surface of the photoconductor drum 51 charged by the first charging process at the first position P1 reaches the third position P3, the developing roller 54 can be brought into contact with the photoconductor drum 51. Therefore, it is possible to prevent the toner from being erroneously moved from the developing roller 54 to the photoconductor drum 51.

In the second exposure process, the photoconductor drum 51 passes through the second position P2 (see FIG. 4) facing the scanner 40 at the portion of the photoconductor drum 51 that is negatively charged by the back charge process. This is a process of exposing the surface of the photoconductor drum 51 by the scanner 40 during one rotation. Specifically, the control device 100 starts the second exposure process after the lapse of the second time T2 described above after starting the back charge process.

Further, the control device 100 ends the second exposure process before starting the second charge process. Specifically, the control device 100 ends the second exposure process after the lapse of the predetermined time TD required for the photoconductor drum 51 to make one rotation after the second exposure process is started.

The control device 100 controls the scanner 40 so as to expose the entire width of the image forming region of the photoconductor drum 51 in the second exposure process. Here, the width of the image forming region means the width of the image forming region in the axial direction of the photoconductor drum 51.

In the second exposure process, it is sufficient that most of the image forming region is exposed. For example, in the second exposure process, a width of about 90% may be exposed with respect to the entire width of the image forming region, a width of about 80% may be exposed, or a width of about 70% may be exposed. You may.

The second charging process is performed while the portion of the photoconductor drum 51 exposed by the second exposure process passes through the first position P1 facing the charging roller 52, while the photoconductor drum 51 makes one rotation. This is a process in which the surface of the photoconductor drum 51 is positively charged by the roller 52. In the second charging process, the control device 100 applies the second charging voltage to the charging roller 52 via the charging voltage application circuit 210. In this embodiment, the second charging voltage is set to the same value as the first charging voltage, that is, a predetermined value V11. However, the present invention is not limited to this, and the second charging voltage may be smaller or larger than the first charging voltage.

Next, the principle of removing the residual charges C1 and C2 will be described with reference to FIG.
As shown in FIG. 6A, when the reverse charge treatment is executed, a negative charge is accumulated on the surface of the photoconductor drum 51, and the potential on the surface of the photosensitive layer 51B becomes a negative potential. Therefore, when the reverse charging process is executed, a second electric field E2 is generated from the grounded raw tube 51A toward the surface of the photosensitive layer 51B. The residual charges C1 and C2 do not easily move from the field even when the second electric field E2 acts on them, and remain.

As shown in FIG. 6B, when the second exposure treatment is executed after the back charge treatment, positive and negative charges C11 and C12 are generated inside the photosensitive layer 51B. Further, the charges C11 and C12 generated by the exposure are easily moved by the action of the electric field.

Of the charges C11 and C12 generated by the exposure, the positive charge C11 moves toward the surface of the photosensitive layer 51B by the action of the second electric field E2. The transferred positive charge C11 is offset by the negative charge charged on the surface of the photosensitive layer 51B, and is offset by the negative residual charge C2 remaining on the surface layer of the photosensitive layer 51B. As a result, as shown in FIG. 6C, a positive residual charge C1 and a negative charge C12 remain in the photosensitive layer 51B.

After that, as shown in FIG. 6D, when the second charging treatment is executed, a positive charge is accumulated on the surface of the photoconductor drum 51, and the potential on the surface of the photosensitive layer 51B becomes a positive potential. Therefore, when the second charging process is executed, a first electric field E1 is generated from the surface of the photosensitive layer 51B toward the raw tube 51A. Then, the negative charge C12 in the photosensitive layer 51B moves toward the surface of the photosensitive layer 51B by the action of the first electric field E1. The transferred negative charge C12 is offset by the positive residual charge C1 remaining on the surface layer of the photosensitive layer 51B. As a result, as shown in FIG. 6E, the residual charges C1 and C2 in the photosensitive layer 51B are substantially removed.

Next, the operation of the control device 100 will be described with reference to FIGS. 7 and 8. Before the control device 100 receives the print command, the stop process is being executed, and the developing roller 54 is separated from the photoconductor drum 51.

As shown in FIG. 7, when the control device 100 receives a print command (START), it first executes a residual charge removal process (S1). As shown in FIG. 8, the control device 100 first starts the back charge process in the residual charge removal process (S11).

When the second time T2 elapses from the start of the back charge process, the control device 100 starts the second exposure process (S12). When the specified time TD elapses from the start of the back charge process, that is, when the photoconductor drum 51 makes one rotation, the control device 100 ends the back charge process (S13).

After that, the control device 100 ends the second exposure process when the predetermined time TD has elapsed from the start of the second exposure process (S14). After completing the second exposure process, the control device 100 starts the second charge process at an appropriate timing (S15). Then, when the predetermined time TD elapses from the start of the second charging process, the control device 100 ends the second charging process (S16) and ends the residual charge removing process.

Returning to FIG. 7, when the control device 100 finishes the residual charge removing process, the control device 100 starts the first charge process (S2). That is, in the present embodiment, the control device 100 continuously executes the first charging process (S2) after the second charging process (S16). Here, in the present embodiment, the first charging voltage at the time of the first charging processing and the second charging voltage at the time of the second charging processing are set to the same value (V11), so that the actual processing in steps S16 and S2 is the same. It is a process that keeps applying the charging voltage. However, when the first charging voltage and the second charging voltage are set to different values, the value of the charging voltage may be switched in step S2.

When the fourth time T4 has elapsed from the start of the first charging process, the control device 100 brings the developing roller 54 into contact with the photoconductor drum 51 by controlling the contact / detachment mechanism TM (S3). That is, in step S3, the control device 100 ends the stop process.

After that, the control device 100 starts the transfer process when the fifth time T5 has elapsed from the start of the first charge process (S4). Here, the fifth time T5 can be, for example, a time equal to or longer than the sum of the first time T1 and the second time T2 described above. By setting T5 ≧ T1 + T2 in this way, the first transfer voltage is applied when the portion of the photoconductor drum 51 charged by the first charging process passes through the fourth position P4 (see FIG. 4). Therefore, it is possible to suppress the influence of the first transfer voltage on the uncharged portion of the photoconductor drum 51.

After step S4, the control device 100 executes the first exposure process (S5). Here, the timing of starting the first exposure process may be any time after the lapse of the second time T2 from the start of the first charging process, but in the present embodiment, it is started after the start of the transfer process.

In step S5, the control device 100 executes the first exposure process based on the image data in the print command, and ends the first exposure process when the last data of the image data has been exposed.

After step S5, the control device 100 ends the transfer process when the first time T1 elapses from the end of the first exposure process (S6). After step S6, the control device 100 ends the first charging process when the third time T3 has elapsed from the end of the transfer process (S7).

After step S7, when the second time T2 elapses from the end of the first charging process, the control device 100 controls the contact / detachment mechanism TM to separate the developing roller 54 from the photoconductor drum 51 (S8). This control is terminated. That is, in step S8, the control device 100 starts the stop process.

Next, an example of the residual charge removing process and the image forming process will be described with reference to FIGS. 9 and 10.
As shown in FIG. 9, when the control device 100 receives the print command (time t1), the control device 100 first executes the back charge process. At this time, the developing roller 54 is separated from the photoconductor drum 51 by the stop processing started at the end of the previous image forming processing.

When the second charging process is executed, the surface of the photoconductor drum 51 is negatively charged as shown in FIG. 10 (a). In the figure, the negative surface potential of the photoconductor drum 51 is virtually shown by a thin broken line, and the positive surface potential is shown by a thin solid line.

Returning to FIG. 9, when the second time T2 elapses from the time t1 when the back charge process is started, the control device 100 starts the second exposure process (time t2). As a result, as shown in FIG. 10B, the portion of the photosensitive layer 51B that is first negatively charged by the charging roller 52 is exposed by the scanner 40 when it reaches the second position P2. Specifically, the second exposure process exposes the entire width of the image forming region.

When the portion negatively charged by the charging roller 52 is exposed by the second exposure process, as shown in FIG. 10 (c), the negative residual charge C2 is removed by the positive charge C11 generated by the exposure. (For details, see FIGS. 6 (b) and 6 (c)). Here, in the figure, in the photosensitive layer 51B, the portion where the residual charges C1 and C2 remain is subjected to high-density hatching, and each time the residual charges C1 and C2 are removed and decreased, the hatching density is applied. Is gradually lowered.

Returning to FIG. 9, the control device 100 ends the back-charging process when the specified time TD corresponding to one rotation of the photoconductor drum 51 elapses from the time t1 when the back-charging process is started (time t4). As a result, the entire circumference of the photoconductor drum 51 is negatively charged by the back charge process. At this time, the state of the electric charge in the photosensitive layer 51B has a distribution as shown in FIG. 10 (d). That is, when the photoconductor drum 51 makes one rotation from the start of the reverse charging process, the initially negatively charged portion returns to the charging roller 52 via the second position P2. Therefore, in the photosensitive layer 51B, the portion on the upstream side of the first position P1 and the downstream side of the second position P2 has been negatively charged and exposed, and the negative residual charge C2 has been removed. It has become.

Returning to FIG. 9, the control device 100 ends the second exposure process when the specified time TD elapses from the time t2 when the second exposure process is started (time t5). As a result, the entire circumference of the photoconductor drum 51 is exposed by the second exposure process. At this time, the charge states in the photosensitive layer 51B have a distribution as shown in FIG. 10 (e). That is, when the photoconductor drum 51 makes one rotation from the start of the second exposure process, the initially negatively charged / exposed portion returns to the second position P2 again. Therefore, the entire photosensitive layer 51B has been negatively charged and exposed, and the negative residual charge C2 has been removed.

Returning to FIG. 9, the control device 100 starts the second charging process at an appropriate timing (time t6) from the time t5 when the second exposure process is completed. When the second charging process is started, the surface of the photoconductor drum 51 is positively charged as shown in FIG. 10 (f). As a result, a first electric field E1 is generated in the photosensitive layer 51B (see FIG. 6D), and the action of the first electric field E1 causes the negative charge C12 generated during the second exposure process to move, resulting in a positive charge. Residual charge C1 is removed.

Returning to FIG. 9, the control device 100 ends the second charging process when the specified time TD elapses from the time t6 when the second charging process is started (time t7). As a result, the entire circumference of the photoconductor drum 51 is affected by the first electric field E1. At this time, the state of the electric charge in the photosensitive layer 51B has a distribution as shown in FIG. 10 (g). That is, when the photoconductor drum 51 makes one rotation from the start of the second charging process, negative charging, exposure, and positive charging are completed for the entire photosensitive layer 51B, so that residual charges C1 and C2 are removed for the entire photosensitive layer 51B. It becomes a state.

After that, as shown in FIG. 9, the image forming process after step S2 in FIG. 7 is executed. That is, after the completion of the second charging process, the control device 100 starts the first charging process (time t7). After that, the control device 100 ends the stop process after the lapse of the fourth time T4 from the time t7, that is, the developing roller 54 is brought into contact with the photoconductor drum 51 (time t8).

Further, the control device 100 starts the transfer process after the lapse of the fifth time T5 from the time t7 (time t9). After the time t9, the control device 100 starts the first exposure process based on the image data at an appropriate timing (time t11).

After that, when the control device 100 finishes the first exposure process based on the image data (time t13), the control device 100 finishes the transfer process after the lapse of the first time T1 from the finished time t13 (time t14). Next, the control device 100 ends the first charging process after the lapse of the third time T3 from the time t14 (time t15). Then, the control device 100 starts the stop process after the lapse of the second time T2 from the time t15, that is, the developing roller 54 is separated from the photoconductor drum 51, and the image forming process is completed.

Based on the above, the following effects can be obtained in the present embodiment.
By performing the back charge treatment and the second exposure treatment for one rotation of the photoconductor drum 51, the second electric field E2 can be applied over the photosensitive layer 51B all around the photoconductor drum 51, and the plus generated by the exposure can be applied. The charge C11 can be moved by the second electric field E2 to remove the negative residual charge C2. Then, by performing the second charging process for one rotation of the photoconductor drum 51, the first electric field E1 can be applied over the photosensitive layer 51B on the entire circumference of the photoconductor drum 51, so that the negative charge generated by the exposure can be applied. The positive residual charge C1 can be removed by moving C12 in the first electric field E1.

Since a negative back-charging voltage was applied to the charging roller 52 in the back-charging process, for example, from the start of the back-charging process to the end of the second exposure process, compared to the form in which the back-charged process is performed using the transfer roller 74. Time can be shortened. Here, when the transfer roller 74 located upstream of the charging roller 52 performs the reverse charging process with respect to the second position P2, the portion negatively charged by the transfer roller 74 reaches the second position P2. The time until is longer than that of the present embodiment. Therefore, as compared with the case where the back charge treatment is performed by such a transfer roller 74, the above-mentioned effect can be obtained in the present embodiment.

Since the developing roller 54 is separated from the photoconductor drum 51 in the stop processing, it is possible to satisfactorily stop the toner from moving from the developing roller 54 to the photoconductor drum 51.

Since the back charge process was started during the stop process, it is possible to satisfactorily suppress the supply of toner to the negatively charged portion. The timing of starting the stop process may be any time as long as the portion negatively charged by the back charge process has not reached the third position P3. In this case, the back charge process can be started during the period when the stop process is not executed, and then the stop process can be started. However, the back charge process is performed during the stop process as in the present embodiment. It is possible to better suppress the supply of toner to the negatively charged portion when the above is started.

Since the second exposure process is started after the lapse of the second time T2 after the reverse charge process is started, for example, the second exposure process is started before the second time T2 elapses from the start of the second charge process. In comparison, it is possible to suppress unnecessary second exposure processing and suppress power consumption.

Since the time for executing the back charge process, the time for executing the second exposure process, and the time for executing the second charge process are set to the same length, it is possible to suppress wasteful execution of each process. can.

[Second Embodiment]
Next, the second embodiment of the present invention will be described in detail with reference to the drawings as appropriate. Since this embodiment is a modification of a part of the processing by the control device 100 according to the first embodiment described above, the same reference numerals are given to the same components and processing as those of the first embodiment. The explanation will be omitted.

As shown in FIG. 11, the control device 100 according to the second embodiment executes the back charge process and the second exposure process after the stop process is started (time t16). The control device 100 executes the back charge process only for the time required for the photoconductor drum 51 to rotate twice, which is 2.TD. Further, the control device 100 starts the second exposure process after the lapse of a predetermined time TP from the time t20 when the back charge process is started (time t21). Here, the predetermined time TP can be expressed by the following equation (5).
TP = TD + D2 / S ... (5)

Since the back-charging device is the charging roller 52 in the present embodiment, the distance DP from the position facing the back-charging device to the position facing the exposure device on the surface of the photoconductor drum 51 is D2. There is.

Further, the control device 100 executes the second exposure process only for the time required for the photoconductor drum 51 to make one rotation (specified time TD).

Next, the operation of the control device 100 according to the second embodiment will be described with reference to FIG. Here, the flowchart shown in FIG. 12 has substantially the same processing of steps S2 to S8 as the flowchart of FIG. 7. Further, in the flowchart shown in FIG. 12, a new process of step S21 is added instead of step S1, and a new process of steps S22 to S25 is added after step S8.

As shown in FIG. 12, when the control device 100 receives the print command (START), the second charging process is first started, and the second charging process is executed only during the specified time TD (S21). After step S21, the control device 100 sequentially executes the processes of steps S2 to S8 described above.

After step S8, the control device 100 starts the back charge process (S22). After step S22, the control device 100 starts the second exposure process after a predetermined time TP has elapsed from the start of the back charge process (S23).

After step S23, the control device 100 ends the back-charging process after the lapse of 2.TD from the start of the back-charging process (S24). After step S24, the control device 100 ends the second exposure process (S25) after the lapse of the predetermined time TD from the start of the second exposure process, and ends the control.

As described above, according to the second embodiment, the following effects can be obtained.
Since the back charge process and the second exposure process are executed after the first charge process for printing, the state of the photosensitive layer 51B can be changed to the state of FIG. 10 (e) after the print is completed. Then, when the printing command is next received, the control device 100 executes the second charging process, so that the state of the photosensitive layer 51B can be changed to the state shown in FIG. 10 (g), so that the first charging process can be performed. Is possible to remove the residual charges C1 and C2 in the photoconductor drum 51 before executing the above.

Since the back charge process and the second exposure process are executed after the first charge process for printing, when the next printing is started, only the second charge process is executed in the photoconductor drum 51. The residual charges C1 and C2 can be removed. Therefore, it is possible to shorten the time from receiving the printing command to starting printing.

Since the back charge treatment was performed for only the time required for the photoconductor drum 51 to rotate twice, TD, the surface of the photoconductor drum 51 positively charged by the first charge treatment was satisfactorily set to a negative surface potential. It can be charged. Further, while the execution time of the back charge process is set to 2 · TD, the execution time of the second exposure process is set to the specified time TD, so that it is possible to suppress the wasteful execution of the second exposure process. can.

[Third Embodiment]
Next, the third embodiment of the present invention will be described in detail with reference to the drawings as appropriate. Since this embodiment is a modification of a part of the structure according to the first embodiment and a part of the control by the control device 100, the same components and processes as those of the first embodiment are used. Will have the same reference numerals and the description thereof will be omitted.

As shown in FIG. 13, the control device 100 according to the third embodiment has the same polarity as the first transfer voltage, that is, a negative second transfer to the transfer roller 74 via the transfer voltage application circuit 240 in the back charge process. Apply voltage. That is, in the present embodiment, the transfer roller 74 functions as a reverse charging device. In this embodiment, as the control of the transfer voltage, for example, constant current control is adopted so that the transfer current flowing through the transfer roller 74 becomes a constant target value.

In the constant current control, the control device 100 monitors the current value flowing through the transfer roller 74, and determines the transfer voltage applied to the transfer roller 74 from the transfer voltage application circuit 240 so that the transfer current becomes a constant target value. , A control signal is output to the transfer voltage application circuit 240 based on the determined transfer voltage. The voltage value of the transfer voltage when the constant current control is executed varies depending on the paper type, environmental conditions (temperature and humidity), the presence or absence of paper, etc., but in FIG. 13, for convenience, it is referred to as the first transfer voltage. The value of the second transfer voltage shall be indicated by the same value (-V2). The value -V2 can be, for example, about -3000V.

The target values of the transfer currents in the transfer process and the back charge process may be the same or different. Further, the control of the transfer voltage is not limited to the constant current control, and may be a constant voltage control in which a constant transfer voltage is applied to the transfer roller 74. In this case, the first transfer voltage and the second transfer voltage may have the same value or different values.

The control device 100 executes the back charge process only for the time required for the photoconductor drum 51 to rotate twice, which is 2.TD. Further, the control device 100 starts the second exposure process after the lapse of a predetermined time TP from the time t30 when the back charge process is started (time t31). Here, the predetermined time TP can be expressed by the following equation (6).
TP = TD + (D2 + D3) / S ... (6)
D2 + D3: A portion of the surface of the photoconductor drum 51 including the second position P2 and the fourth position P4 (see FIG. 4), upstream of the second position P2 and more than the fourth position P4. Perimeter of the downstream part

That is, in this embodiment, since the back-charging device is the transfer roller 74, the distance DP from the position facing the back-charging device to the position facing the exposure device on the surface of the photoconductor drum 51 is D2 + D3. ..

Next, the operation of the control device 100 according to the third embodiment will be described with reference to FIG. Here, the flowchart shown in FIG. 14 is a partially modified version of the residual charge removal process (flow chart in FIG. 8) according to the first embodiment. The flowchart shown in FIG. 14 has substantially the same processing of steps S14 to S16 as the flowchart of FIG. Further, in the flowchart shown in FIG. 15, new steps S31 to S33 are added.

Upon receiving the print command, the control device 100 executes the processing of the flowchart shown in FIG. 7. When the residual charge removal process is executed, the control device 100 starts the process of the flowchart shown in FIG. 14 (S1).

As shown in FIG. 14, in the residual charge removing process, the control device 100 first starts the back charge process using the transfer roller 74 (S31). After step S31, the control device 100 starts the second exposure process after a predetermined time TP has elapsed from the start of the back charge process (S32).

After step S32, the control device 100 ends the back-charging process after the lapse of 2.TD from the start of the back-charging process (S33). After step S33, the control device 100 sequentially executes the processes of steps S14 to S16 described above.

As described above, according to the third embodiment, it is possible to obtain substantially the same effect as that of the first embodiment.
Further, as in each of the above-described embodiments, the reverse charging device is a transfer roller 74 or a charging roller 52, that is, a member that contributes to printing, for example, a case where the reverse charging device is a member that does not contribute to printing. In comparison, the increase in the number of parts can be suppressed.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings as appropriate. Since this embodiment is a modification of a part of the back-charging process according to the second embodiment described above, the same components and processes as those of the second embodiment are designated by the same reference numerals. , The description thereof will be omitted.

As shown in FIG. 15, the control device 100 according to the fourth embodiment executes the back charge process by applying a negative second transfer voltage to the transfer roller 74. Other processes of the control device 100 are the same as those of the second embodiment. The flowchart for operating the control device 100 is the same as the flowchart of FIG. Specifically, the control target in the back charge process in step S22 of FIG. 12 is only the transfer roller 74. According to this fourth embodiment, the same effect as that of the second embodiment can be obtained.

The present invention is not limited to each of the above embodiments, and can be used in various forms as illustrated below.
In the second and third embodiments, TP = TD + DP / S, but the present invention is not limited to this, and TP ≧ TD + DP / S may be used.

The timing for separating the developing rollers 54, that is, the timing for starting the stop processing may be any time after the portion last exposed by the first exposure process based on the image data reaches the developing rollers 54. Similarly, the timing of the end of the stop process may be any time after the portion charged by the charging roller 52 reaches the position facing the developing roller 54.

The timing and execution time of the start of the back charge process, the second exposure process, and the second charge process are not limited to each of the above-described embodiments, and can be appropriately set. For example, in the first embodiment, the timing of starting the back charge process and the second exposure process may be simultaneous.

The first charging process and the second charging process may be performed continuously in each embodiment, or a period for setting the charging voltage to 0 is provided between the first charging process and the second charging process, respectively. It may be separated. Similarly, the first exposure process and the second exposure process, the back charge process and the first charge process, and the like may be performed continuously or separately.

The developer is not limited to the positively charged toner, and may be a negatively charged toner. When a negatively charged toner is used, the polarity of each voltage described above may be changed to the opposite polarity.

The photoconductor is not limited to the photoconductor drum 51, and may be, for example, a belt-shaped photoconductor.

The charger is not limited to the charging roller 52, and may be, for example, a corona discharge type charger provided at a position away from the photoconductor. That is, it may be a charger including a charging wire and a grid electrode.

The exposure device is not limited to the scanner 40, and may be, for example, an LED unit that exposes the photoconductor with an LED, a static eliminator that eliminates static electricity on the surface of the photoconductor, or the like.

The developing device is not limited to the developing device 520 provided with the developing roller 54 in contact with the photoconductor drum 51, and may be, for example, a non-contact type developing device arranged away from the photoconductor.

The transfer member is not limited to the transfer roller 74, and may be, for example, a non-contact transfer member arranged apart from the photoconductor drum.

The reverse charging device is not limited to the charging roller 52 and the transfer roller 74, and may be, for example, a cleaning blade 57, the above-mentioned non-contact type transfer member, or the like.

The stop processing is not limited to the processing performed by contacting / separating the developing rollers 54, for example, by switching the developing voltage applied to the developing rollers to a voltage smaller than the surface potential of the exposed portion of the photoconductor drum. The supply of toner from the rollers to the photoconductor drum may be stopped.

The image forming apparatus is not limited to the color printer 1, and may be, for example, a monochrome printer, a copying machine, a multifunction device, or the like.

The transfer medium is not limited to the paper P, and may be, for example, a belt in contact with the photoconductor drum in an intermediate transfer type printer.

Further, each element described in the above-described embodiment and modification may be arbitrarily combined and carried out.

1 Color printer 40 Scanner 51 Photoreceptor drum 51B Photosensitive layer 52 Charging roller 54 Developing roller 100 Control device 520 Developer P paper

Claims (11)

A photoconductor having a photosensitive layer and
A charger that charges the surface of the photoconductor to the first polarity,
A reverse charging device that charges the surface of the photoconductor to a second polarity opposite to the first polarity.
An exposure device that exposes the surface of the photoconductor and
A developer that supplies a developer to the photoconductor and
Equipped with a control device,
The control device is
A first charging process in which the surface of the photoconductor is charged to the first polarity by the charging device,
The first exposure treatment of exposing the surface of the photoconductor charged by the first charging treatment with the exposure apparatus to form an electrostatic latent image on the surface.
A developing process in which a developer is supplied to the electrostatic latent image by the developer to form a developer image on the surface of the photoconductor.
A transfer process for transferring the developer image to a transfer medium, and
A reverse charging treatment in which the surface of the photoconductor is charged to the second polarity by the back charging device at least while the photoconductor makes two rotations in a period different from the execution period of the transfer treatment.
The supply of the developer from the developer to the photoconductor is stopped during the period in which the portion of the photoconductor charged to the second polarity by the reverse charge process passes through the position facing the developer. Stop processing and
During the period in which the portion of the photoconductor, which is charged to the second polarity by the back charge treatment, passes through the position facing the exposure device, the exposure device causes the exposure device to make at least one rotation of the photoconductor. The second exposure process for exposing the surface of the photoconductor, the second exposure process started after the lapse of a predetermined time TP from the start of the back charge process, and the second exposure process.
During the period in which the portion of the photoconductor exposed by the second exposure process passes through the position facing the charger, the surface of the photoconductor is exposed to the surface of the photoconductor by the charger for at least one rotation of the photoconductor. The second charging process of charging to the first polarity is executed.
The predetermined time TP is TD for the time for one rotation of the photoconductor, DP for the distance from the position facing the reverse charging device on the surface of the photoconductor to the position facing the exposure device, and the circumference of the photoconductor. When the speed is S,
TP ≧ TD + DP / S
An image forming apparatus characterized by satisfying. A charging voltage application circuit for applying a charging voltage to the charging device is provided.
The reverse charging device is the charging device.
The control device is
In the first charging process, the first charging voltage is applied to the charger via the charging voltage application circuit.
The image forming apparatus according to claim 1, wherein in the reverse charging process, a reverse charging voltage having a polarity opposite to that of the first charging voltage is applied to the charging device via the charging voltage application circuit. A transfer member that transfers the developer on the surface of the photoconductor to a transfer medium, and
A transfer voltage application circuit that applies a transfer voltage to the transfer member is provided.
The reverse charging device is the transfer member.
The control device is
In the transfer process, a first transfer voltage is applied to the transfer member via the transfer voltage application circuit.
The image forming apparatus according to claim 1, wherein in the reverse charging process, a second transfer voltage having the same polarity as the first transfer voltage is applied to the transfer member via the transfer voltage application circuit. The image forming apparatus according to any one of claims 1 to 3, wherein the control device separates the developer from the photoconductor in the stop process. The control device is
The reverse charge treatment is performed for the time that the photoconductor makes two rotations, and then the back charge treatment is performed.
The image forming apparatus according to any one of claims 1 to 4, wherein the second exposure process is performed only for a period of one rotation of the photoconductor. Any one of claims 1 to 5, wherein the control device starts the back charge process after stopping the supply of the developer from the developer to the photoconductor by the stop process. The image forming apparatus according to the section. A photoconductor having a photosensitive layer and
A charger that charges the surface of the photoconductor to the first polarity,
A reverse charging device that charges the surface of the photoconductor to a second polarity opposite to the first polarity.
An exposure device that exposes the surface of the photoconductor and
A developer that supplies a developer to the photoconductor and
A control method using the control device in an image forming device including a control device.
The first charging step of charging the surface of the photoconductor to the first polarity by the charging device,
The first exposure step of exposing the surface of the photoconductor charged by the first charging step with the exposure apparatus to form an electrostatic latent image on the surface.
A developing step of supplying a developer to the electrostatic latent image by the developer to form a developer image on the surface of the photoconductor.
A transfer step of transferring the developer image to a transfer medium,
A back-charging step of charging the surface of the photoconductor to the second polarity by the back-charging device for at least two rotations of the photoconductor in a period different from the execution period of the transfer step.
The supply of the developer from the developer to the photoconductor is stopped during the period in which the portion of the photoconductor, which is charged to the second polarity by the reverse charging step, passes through the position facing the developer. Stopping process and
During the period in which the portion of the photoconductor, which is charged to the second polarity by the reverse charging step, passes through the position facing the exposure device, the exposure device causes the exposure device to make at least one rotation of the photoconductor. The second exposure step of exposing the surface of the photoconductor, the second exposure step starting after the lapse of a predetermined time TP from the start of the back charge step, and the second exposure step.
During the period in which the portion of the photoconductor exposed by the second exposure step passes through the position facing the charger, the surface of the photoconductor is exposed to the surface of the photoconductor by the charger for at least one rotation of the photoconductor. The second charging step of charging to the first polarity is provided.
The predetermined time TP is TD for the time for one rotation of the photoconductor, DP for the distance from the position facing the reverse charging device on the surface of the photoconductor to the position facing the exposure device, and the circumference of the photoconductor. When the speed is S,
TP ≧ TD + DP / S
A control method characterized by satisfying. A photoconductor having a photosensitive layer and
A charger that charges the surface of the photoconductor to the first polarity,
A reverse charging device that charges the surface of the photoconductor to a second polarity opposite to the first polarity.
An exposure device that exposes the surface of the photoconductor and
A developer that supplies a developer to the photoconductor and
A program for operating the control device in an image forming device including the control device.
The control device
A means for performing a first charging process in which the surface of the photoconductor is charged to the first polarity by the charger.
A means for executing the first exposure process of exposing the surface of the photoconductor charged by the first charge process with the exposure apparatus to form an electrostatic latent image on the surface.
A means for executing a developing process in which a developer is supplied to the electrostatic latent image by the developer to form a developer image on the surface of the photoconductor.
A means for performing a transfer process for transferring the developer image to a transfer medium,
A means for executing a back-charging treatment in which the surface of the photoconductor is charged to the second polarity by the back-charging device for at least two rotations of the photoconductor in a period different from the execution period of the transfer treatment.
The supply of the developer from the developer to the photoconductor is stopped during the period in which the portion of the photoconductor charged to the second polarity by the reverse charge process passes through the position facing the developer. And the means to execute the stop processing
During the period in which the portion of the photoconductor, which is charged to the second polarity by the back charge treatment, passes through the position facing the exposure device, the exposure device causes the exposure device to make at least one rotation of the photoconductor. A means for executing a second exposure process for exposing the surface of the photoconductor, which is a second exposure process that starts after a lapse of a predetermined time TP from the start of the back charge process.
During the period in which the portion of the photoconductor exposed by the second exposure process passes through the position facing the charger, the surface of the photoconductor is exposed to the surface of the photoconductor by the charger for at least one rotation of the photoconductor. It functions as a means for executing the second charging process of charging to the first polarity.
The predetermined time TP is TD for the time for one rotation of the photoconductor, DP for the distance from the position facing the reverse charging device on the surface of the photoconductor to the position facing the exposure device, and the circumference of the photoconductor. When the speed is S,
TP ≧ TD + DP / S
A program characterized by satisfying. A photoconductor having a photosensitive layer and
A charger that charges the surface of the photoconductor to the same polarity as the developer and a primary polarity.
A reverse charging device that charges the surface of the photoconductor to a second polarity opposite to the first polarity.
An exposure device that exposes the surface of the photoconductor and
A developer that supplies a developer to the photoconductor and
Equipped with a control device,
The control device is
It is possible to perform an image forming process for forming a developer image on a transfer medium and a residual charge removing process for removing the residual charge remaining in the photosensitive layer.
The residual charge removal treatment is
A back-charging process in which the surface of the photoconductor is charged to the second polarity by the back-charging device at least while the photoconductor makes two rotations.
The supply of the developer from the developer to the photoconductor is stopped during the period in which the portion of the photoconductor charged to the second polarity by the reverse charge process passes through the position facing the developer. Stop processing and
During the period in which the portion of the photoconductor, which is charged to the second polarity by the back charge treatment, passes through the position facing the exposure device, the exposure device causes the exposure device to make at least one rotation of the photoconductor. An exposure process for exposing the surface of the photoconductor, the exposure process started after a predetermined time TP has elapsed from the start of the back charge process, and the exposure process.
During a period in which the portion of the photoconductor exposed by the exposure process passes through a position facing the charger, the surface of the photoconductor is exposed to the surface of the photoconductor by the charger for at least one rotation of the photoconductor. Including charging treatment to charge to one polarity,
The predetermined time TP is TD for the time for one rotation of the photoconductor, DP for the distance from the position facing the reverse charging device on the surface of the photoconductor to the position facing the exposure device, and the circumference of the photoconductor. When the speed is S,
TP ≧ TD + DP / S
An image forming apparatus characterized by satisfying. The control device is
The image forming apparatus according to claim 9, wherein the exposure process is performed only for a period of one rotation of the photoconductor. The control device is
The image forming apparatus according to claim 9, wherein the back charge process is performed only for a time during which the photoconductor makes two rotations.

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